I dunno Chris. Acting is all about pretending, isn't it? When a male actor is 'making love' with a beautiful female actress, they aren't really as 'intimate' as you appear to think.

Besides, it's not unknown for a man to want sex with no emotional baggage attached. So what I'm saying is that when the actor was kissing her ( or even when the diplomat was Kissinger ) , he didn't really mean it. If you wanna know if he loves you so, it's in his kiss....

I want to believe that the characters on the screen are madly in love, especially Nick Cage&what's-her-name in Sleepless in Seattle...if you're female, a good cry as a response to a sappy movie changes your biochemistry and really does make you feel better - sorry guys, the research I read was only done with females subjects.  I want to believe that I can have a love that is as grand and timeless as the one on the screen, but I don't really expect Nick Cage to knock on my door in that wonderfully brooding black costume and offer to give up Heaven if I'd just love him.  
So, if the kiss (etc) is not convincing, I won't want to watch the movie, if no one fills the seats at the theater or buys the popcorn, my pal Nick is out of a job, so the love scenes (yes, I know they're 'sex scenes') are made to look as though there are only two people in a darkened room...<screech of brakes on a dry road>...but wait a minute... some of these steamy shots are filmed with only one actor/actress, and even if they're together, there are multiple takes (so you kiss for 15 seconds, then stop while someone makes a change to something), there are the strategically placed sheets (which sometimes cover strategically placed itsy-bitsy articles of clothing), and there are the people who run the cameras, the lights, the microphones, the folks who touch up costumes, make-up & hair, then there are the gaffers, the best boys (does anyone actually know what a "Best Boy" is??)...sorry...I digressed for just a second...anyway, back to the massive number of people who are in the very big room...throw in the differences in the physiological responses of males & females...

Why, Yes, Virginia, there is a summary, and here it comes...I think the sexual activity in a sexual scene could be sexually stimulating for a male as well as for a female, but I think it'd be about as satisfying as being 15 in the back of a car making out...it's not like they're able to complete actual intercourse in a 'regular'movie.  

Is it "real"?  I doubt it, but I'm willing to pretend it is for the 117 minutes it's on the screen.

In music there is also the acting while playing and I believe it has nothing to do with what the performers actually feel for each other in real life. For example I know members of a famous quartet who can't stand each other, and each takes the train in a different wagon so that they don't see each other. Yet in the evening, they all play together in perfect harmony, sometimes even "making love" to each other musically speaking.

I never had this kind of experience (hate in life, love on stage), but when I play with others, I have so many practical things to think about that a passage can seem like a love idyll between us and I would be in fact concentrating on completely different and practical things (and I'm positive they can say the same). These things are mostly technical, e.g. how to play soft but not too soft so as to sustain the others well, how to make the arpeggio sound smooth with no accent on the thumb, how to get to the chord exactly at the right moment for the last note together and so on and so on.

So I definitely think that there is a separation between the professional act and real life, even if when things are going extremely well and we managed to play together with inspiration, there is no denying the feeling of satisfaction and mutual sympathy, but it's of another nature. Maybe like a sport's team that managed to win a game?